Adhesive composition, adhesive layer, polarizing film provided with adhesive layer, and image formation device

ABSTRACT

A pressure-sensitive adhesive composition comprising (A) a (meth)acryl-based polymer, (B1) an ionic compound comprising a cation component and an anion component having an organic group of three or more carbon atoms, and (B2) an ionic compound comprising a cation component and an anion component having an organic group of two or less carbon atoms. The anion component having an organic group of three or more carbon atoms is preferably at least one of anion components represented by formula (1):
 
(C n F 2n+1 SO 2 ) 2 N −   (1)
         in formula (1), n is an integer of 3 to 10, formula (2):
 
CF 2 (C m F 2m SO 2 ) 2 N −   (2)
   in formula (2), m is an integer of 2 to 10, formula (3):
 
 −O   3 S(CF 2 ) l SO 3   −   (3)
   in formula (3), l is an integer of 3 to 10, and formula (4):
 
(C p F 2p+1 SO 2 )N − (C q F 2q+1 SO 2 )  (4)
   in formula (4), p and q are each an integer of 2 to 10.

TECHNICAL FIELD

The present invention relates to a pressure-sensitive adhesivecomposition with good antistatic properties, a pressure-sensitiveadhesive layer made from such a pressure-sensitive adhesive composition,and a pressure-sensitive adhesive layer-bearing polarizing filmincluding a polarizing film and such a pressure-sensitive adhesivelayer. The present invention also relates to an image display devicesuch as a liquid crystal display device, an organic electroluminescent(EL) display device, or a plasma display panel (PDP) produced with sucha pressure-sensitive adhesive layer-bearing polarizing film.

BACKGROUND ART

Liquid crystal display devices and other display devices have animage-forming mechanism including polarizing elements placed asessential components on both sides of a liquid crystal cell, andgenerally, polarizing films are attached as the polarizing elements. Apressure-sensitive adhesive is generally used to bond such polarizingfilms to a liquid crystal cell. When such polarizing films are bonded toa liquid crystal cell, a pressure-sensitive adhesive is generally usedto bond the materials together so that optical loss can be reduced. Insuch a case, the pressure-sensitive adhesive is provided in advance as apressure-sensitive adhesive layer on one side of a polarizing film, andthe resulting pressure-sensitive adhesive layer-bearing polarizing filmis generally used because it has some advantages such as no need for adrying process to fix the polarizing film. A release film is generallyattached to the pressure-sensitive adhesive layer of thepressure-sensitive adhesive layer-bearing polarizing film.

When a liquid crystal display device is manufactured, thepressure-sensitive adhesive layer-bearing polarizing film is bonded to aliquid crystal cell. In this process, static electricity is generatedwhen the release film is peeled off from the pressure-sensitive adhesivelayer of the pressure-sensitive adhesive layer-bearing optical film. Thestatic electricity generated in this manner may affect the orientationof the liquid crystal in the liquid crystal display device to cause afailure. The static electricity may also cause display unevenness whenthe liquid crystal display device operates. For example, the staticgeneration can be suppressed when an antistatic layer is formed on theouter surface of the polarizing film. In this case, however, the effectis not high, and there is still a problem in that static generationcannot be fundamentally prevented. To suppress static generation in afundamental position, therefore, the pressure-sensitive adhesive layeris required to have an antistatic function. Concerning means forproviding an antistatic function to a pressure-sensitive adhesive layer,for example, it is proposed that an ionic compound should be added to apressure-sensitive adhesive used to form a pressure-sensitive adhesivelayer (Patent Documents 1 to 6).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2005-306937

Patent Document 2: JP-W-2006-111846

Patent Document 3: JP-A-2008-517138

Patent Document 4: JP-W-2010-523806

Patent Document 5: JP-A-2011-016990

Patent Document 6: JP-A-2011-017000

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Patent Documents 1 and 2 disclose that a pressure-sensitive adhesivelayer with an antistatic function can be made from a pressure-sensitiveadhesive composition containing an ionic compound having abis(pentafluoroethanesulfonyl)imide anion component. Patent Documents 3and 4 disclose that a pressure-sensitive adhesive layer with anantistatic function can be made from a pressure-sensitive adhesivecomposition containing an ionic compound having abistrifluoromethanesulfonimide or bistrifluoroethanesulfonimide anioncomponent. However, the pressure-sensitive adhesive layers made fromthese pressure-sensitive adhesive compositions containing an ioniccompound can increase in surface resistance and degrade in antistaticfunction when exposed to conditions exceeding normal temperature andnormal humidity, such as hot and humid conditions at 60° C. and 90% RHor at 60° C. and 95% RH.

Patent Documents 5 and 6 disclose that a pressure-sensitive adhesivecomposition containing an ionic compound having an imide anion with acarbon atom-containing perfluoroalkyl group cannot form apressure-sensitive adhesive layer with a sufficiently improvedantistatic function, whereas a pressure-sensitive adhesive compositioncontaining an ionic compound having a bis(fluorosulfonyl)imide anion canform a pressure-sensitive adhesive layer with an improved antistaticfunction. Unfortunately, the disclosures in these patent documents donot aim to suppress an increase in surface resistance after a humiditytest. These patent documents do not specifically disclose or suggest anysurface resistance after exposure to hot and humid conditions.

As far as the present inventors know, there has been no report yetsuggesting that a humidity test-induced increase in the surfaceresistance of a pressure-sensitive adhesive layer made from apressure-sensitive adhesive composition should be suppressed, and whatis more, there has been no report yet suggesting that a humiditytest-induced increase in the surface resistance should be suppressedwhile the initial surface resistance should be kept low.

The present invention has been made in view of the circumstancesdescribed above. It is an object of the present invention to provide apressure-sensitive adhesive composition whose durability and other mainproperties are high and which can form a pressure-sensitive adhesivelayer having both a lower surface resistance (particularly, a lowerinitial surface resistance) and higher moisture durability of antistaticfunction, and to provide such a pressure-sensitive adhesive layer and apolarizing film provided with such a pressure-sensitive adhesive layer.

It is another object of the present invention to provide an imagedisplay device including such a pressure-sensitive adhesivelayer-bearing polarizing film.

Means for Solving the Problems

When a common ionic compound is used to impart an antistatic function toa pressure-sensitive adhesive layer, the surface resistance of thepressure-sensitive adhesive layer can significantly increase after ahumidity test, so that the antistatic function can be lost. On the otherhand, an ionic compound having an anion component with a relativelyhigh-molecular-weight organic group or an ionic compound having an anioncomponent with a cyclic structure-containing organic group can be usedfor a pressure-sensitive adhesive layer. In this case, the antistaticfunction can be prevented from decreasing even after a humidity test,but to decrease the initial surface resistance, it is necessary to add alarge amount of the ionic compound, which can have an adverse effect onother properties such as durability when it is used by itself. As aresult of intensive studies based on these things, the present inventorshave found that when an ionic compound having a high-molecular anioncomponent is used in combination with an ionic compound having alow-molecular anion component, a decrease in initial surface resistanceand suppression of a humidification-induced increase in surfaceresistance can be achieved at the same time with no adverse effect ondurability and other properties. The present invention, which has beenaccomplished as a result of the studies, has the following features toachieve the objectives.

Specifically, the present invention is directed to a pressure-sensitiveadhesive composition containing (A) a (meth)acryl-based polymer, (B1) anionic compound including a cation component and an anion componenthaving an organic group of three or more carbon atoms, and (B2) an ioniccompound including a cation component and an anion component having anorganic group of two or less carbon atoms.

In the pressure-sensitive adhesive composition, the anion componenthaving an organic group of three or more carbon atoms is at least one ofanion components represented by formula (1):(C_(n)F_(2n+1)SO₂)₂N⁻  (1)

in formula (1), n is an integer of 3 to 10, formula (2):CF₂(C_(m)F_(2m)SO₂)₂N⁻  (2)

in formula (2), m is an integer of 2 to 10, formula (3):⁻O₃S(CF₂)_(l)SO₃ ⁻  (3)

in formula (3), l is an integer of 3 to 10, and formula (4):(C_(p)F_(2p+1)SO₂)N⁻(C_(q)F_(2q+1)SO₂)  (4)in formula (4), p and q are each an integer of 2 to 10.

In the pressure-sensitive adhesive composition, the cation component ofat least one of the ionic compound (B1) and the ionic compound (B2) ispreferably a lithium cation.

In the pressure-sensitive adhesive composition, the anion componenthaving an organic group of three or more carbon atoms is preferably atleast one of a bis(heptafluoropropanesulfonyl)imide anion, abis(nonafluorobutanesulfonyl)imide anion, acyclo-hexafluoropropane-1,3-bis(sulfonyl)imide anion, and ahexafluoropropane-1,3-disulfonic acid anion.

The pressure-sensitive adhesive composition preferably contains 0.001 to4 parts by weight of the ionic compound (B1) and 0.001 to 4 parts byweight of the ionic compound (B2) based on 100 parts by weight of the(meth)acryl-based polymer (A).

In the pressure-sensitive adhesive composition, the (meth)acryl-basedpolymer (A) preferably contains monomer units derived from an alkyl(meth)acrylate and a hydroxyl group-containing monomer. The(meth)acryl-based polymer (A) also preferably contains monomer unitsderived from an alkyl (meth)acrylate and a carboxyl group-containingmonomer.

The pressure-sensitive adhesive composition preferably further containsa crosslinking agent (C). The pressure-sensitive adhesive compositionpreferably contains 0.01 to 20 parts by weight of the crosslinking agent(C) based on 100 parts by weight of the (meth)acryl-based polymer (A).The crosslinking agent (C) is more preferably at least one of anisocyanate compound and a peroxide.

The pressure-sensitive adhesive composition preferably further contains0.001 to 5 parts by weight of (D) a silane coupling agent based on 100parts by weight of the (meth)acryl-based polymer (A) or preferablyfurther contains 0.001 to 10 parts by weight of (E) a polyether-modifiedsilicone based on 100 parts by weight of the (meth)acryl-based polymer(A).

In the pressure-sensitive adhesive composition, the (meth)acryl-basedpolymer (A) preferably has a weight average molecular weight of 500,000to 3,000,000.

The present invention is also directed to a pressure-sensitive adhesivelayer including a product made from the pressure-sensitive adhesivecomposition having any of the above features.

The present invention is also directed to a pressure-sensitive adhesivelayer-bearing polarizing film including at least a polarizing film andthe pressure-sensitive adhesive layer. The pressure-sensitive adhesivelayer-bearing polarizing film preferably has an adhesion-facilitatinglayer between the polarizing film and the pressure-sensitive adhesivelayer.

The present invention is also directed to an image display deviceincluding at least one piece of the pressure-sensitive adhesivelayer-bearing polarizing film.

Effect of the Invention

If an ionic compound is added to a pressure-sensitive adhesivecomposition containing an acryl-based polymer as a base polymer, anantistatic function can be imparted to the pressure-sensitive adhesivecomposition. On the other hand, if an ionic compound exists on thesurface of a pressure-sensitive adhesive layer, the adhering strengthbetween the pressure-sensitive adhesive layer and the adherend maydecrease, and after a test of exposure to hot and humid conditions, thesurface resistance of the pressure-sensitive adhesive layer may increaseso that the antistatic function may be lost.

The pressure-sensitive adhesive composition according to the presentinvention contains ionic compounds capable of imparting an antistaticfunction in addition to the (meth)acryl-based polymer (A), and thepressure-sensitive adhesive layer made from the pressure-sensitiveadhesive composition has a good antistatic function. Particularly sincethe pressure-sensitive adhesive composition according to the presentinvention contains two types of ionic compounds (B1) and (B2), thepressure-sensitive adhesive layer made of the pressure-sensitiveadhesive composition and the polarizing film provided with thepressure-sensitive adhesive layer not only have (i) a high level ofdurability and other main properties but also have both (ii) a lowersurface resistance (particularly, a lower initial surface resistance)and (iii) higher moisture durability of antistatic function.

MODE FOR CARRYING OUT THE INVENTION

The pressure-sensitive adhesive composition according to the presentinvention contains (A) a (meth)acryl-based polymer as a base polymer.The (meth)acryl-based polymer (A) contains, as a main component, amonomer unit derived from an alkyl (meth)acrylate. As used herein, theterm “(meth)acrylate” refers to acrylate and/or methacrylate, and“(meth)” is used in the same meaning in the specification.

An alkyl (meth)acrylate may be used to form the main skeleton of the(meth)acryl-based polymer (A). For example, such an alkyl (meth)acrylatemay have a linear or branched alkyl group of 1 to 18 carbon atoms. Forexample, such an alkyl group may be methyl, ethyl, propyl, isopropyl,butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl,isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl,tridecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, or the like.These groups may be used alone or in any combination. Such alkyl groupspreferably have an average number of carbon atoms of 3 to 9.

An aromatic ring-containing alkyl (meth)acrylate such as phenoxyethyl(meth)acrylate or benzyl (meth)acrylate may also be used forpressure-sensitive adhesive properties, durability, control ofretardation, control of refractive index, or other purposes. Thearomatic ring-containing alkyl (meth)acrylate may be used to produce apolymer for use in mixing with the (meth)acryl-based polymer mentionedabove. In view of transparency, however, the aromatic ring-containingalkyl (meth)acrylate is preferably used together with the alkyl(meth)acrylate to produce a copolymer.

Concerning the (meth)acryl-based polymer (A), the content of thearomatic ring-containing alkyl (meth)acrylate in all the monomers (100%by weight) used to form the (meth)acryl-based polymer (A) may be 50% byweight or less. The content of the aromatic ring-containing alkyl(meth)acrylate is preferably from 1 to 35% by weight, more preferablyfrom 5 to 30% by weight, even more preferably from 10 to 25% by weight.

To improve tackiness or heat resistance, one or more copolymerizablemonomers having an unsaturated double bond-containing polymerizablefunctional group such as a (meth)acryloyl group or a vinyl group may beintroduced into the (meth)acryl-based polymer (A) by copolymerization.Examples of such copolymerizable monomers include hydroxylgroup-containing monomers such as 2-hydroxyethyl (meth)acrylate,3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate,6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate,10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and(4-hydroxymethylcyclohexyl)methyl acrylate; carboxyl group-containingmonomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate,carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid,and crotonic acid; acid anhydride group-containing monomers such asmaleic anhydride and itaconic anhydride; caprolactone adducts of acrylicacid; sulfonic acid group-containing monomers such as styrenesulfonicacid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonicacid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate,and (meth)acryloyloxynaphthalenesulfonic acid; and phosphategroup-containing monomers such as 2-hydroxyethylacryloyl phosphate.

Examples of such monomers for modification also include (N-substituted)amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide,N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, andN-methylolpropane(meth)acrylamide; alkylaminoalkyl (meth)acrylatemonomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and tert-butylaminoethyl (meth)acrylate; alkoxyalkyl(meth)acrylate monomers such as methoxyethyl (meth)acrylate andethoxyethyl (meth)acrylate; succinimide monomers such asN-(meth)acryloyloxymethylenesuccinimide,N-(meth)acryloyl-6-oxyhexamethylenesuccinimide,N-(meth)acryloyl-8-oxyoctamethylenesuccinimide, andN-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide,N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; anditaconimide monomers such as N-methylitaconimide, N-ethylitaconimide,N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide,N-cyclohexylitaconimide, and N-laurylitaconimide.

Examples of modifying monomers that may also be used include vinylmonomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone,methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine,vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole,vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene,α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such asacrylonitrile and methacrylonitrile; epoxy group-containing acrylicmonomers such as glycidyl (meth)acrylate; glycol acrylate monomers suchas polyethylene glycol (meth)acrylate, polypropylene glycol(meth)acrylate, methoxyethylene glycol (meth)acrylate, andmethoxypolypropylene glycol (meth)acrylate; and acrylic ester monomerssuch as tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate,silicone (meth)acrylate, and 2-methoxyethyl acrylate. Examples alsoinclude isoprene, butadiene, isobutylene, vinyl ether, etc.

Copolymerizable monomers other than the above include silane monomerscontaining a silicon atom. Examples of such silane monomers include3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane,vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane,4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane,8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane,10-acryloyloxydecyltrimethoxysilane,10-methacryloyloxydecyltriethoxysilane, and10-acryloyloxydecyltriethoxysilane.

Examples of copolymerizable monomers that may also be used includepolyfunctional monomers having two or more unsaturated double bonds suchas those in (meth)acryloyl groups or vinyl groups, which include(meth)acrylic esters of polyhydric alcohols, such as tripropylene glycoldi(meth)acrylate, tetraethylene glycol di(meth)acrylate,1,6-hexanedioldi(meth)acrylate, bisphenol A diglycidyl etherdi(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,dipentaerythritol hexa(meth)acrylate, and caprolactone-modifieddipentaerythritol hexa(meth)acrylate; and polyester (meth)acrylates,epoxy (meth)acrylates, urethane (meth)acrylates, or other compoundshaving a polyester, epoxy, or urethane skeleton, to which two or moreunsaturated double bonds are added in the form of functional groups suchas (meth)acryloyl groups or vinyl groups in the same manner as theconstituent monomers.

Concerning the weight contents of all the monomers used to form the(meth)acryl-based polymer (A), the alkyl (meth)acrylate should be a maincomponent, and the content of the copolymerizable monomer is preferably,but not limited to, 0 to about 20%, more preferably about 0.1 to about15%, even more preferably about 0.1 to about 10%, based on the totalweight of all the monomers used to form the (meth)acryl-based polymer(A).

Among these copolymerizable monomers, hydroxyl group-containing monomersand carboxyl group-containing monomers are preferably used in view oftackiness or durability. A hydroxyl group-containing monomer may be usedin combination with a carboxyl group-containing monomer. When thepressure-sensitive adhesive composition contains a crosslinking agent,these copolymerizable monomers can serve as reactive sites to thecrosslinking agent. Such hydroxyl group-containing and carboxylgroup-containing monomers are highly reactive with intermolecularcrosslinking agents and therefore are preferably used to improve thecohesiveness or heat resistance of the resulting pressure-sensitiveadhesive layer. Hydroxyl group-containing monomers are advantageous interms of reworkability, and carboxyl group-containing monomers areadvantageous in providing both durability and reworkability.

When a hydroxyl group-containing monomer is added as a copolymerizablemonomer, the content thereof is preferably from 0.01 to 15% by weight,more preferably from 0.03 to 10% by weight, even more preferably from0.05 to 7% by weight. When a carboxyl group-containing monomer is addedas a copolymerizable monomer, the content thereof is preferably from0.05 to 10% by weight, more preferably from 0.1 to 8% by weight, evenmore preferably from 0.2 to 6% by weight.

In the present invention, the (meth)acryl-based polymer (A) usedpreferably has a weight average molecular weight in the range of 500,000to 3,000,000. In view of durability, particularly, heat resistance, the(meth)acryl-based polymer (A) used preferably has a weight averagemolecular weight of 700,000 to 2,700,000. It more preferably has aweight average molecular weight of 800,000 to 2,500,000. A weightaverage molecular weight of less than 500,000 is not preferred in viewof heat resistance. If the weight average molecular weight is more than3,000,000, a large amount of a diluent solvent can be necessary foradjusting the viscosity to be suitable for coating, which may increasecost and is not preferred. The weight average molecular weight refers toa polystyrene-equivalent molecular weight as measured and calculatedusing gel permeation chromatography (GPC).

The (meth)acryl-based polymer (A) described above can be produced by amethod appropriately selected from known methods such as solutionpolymerization, bulk polymerization, emulsion polymerization, andvarious types of radial polymerization. The resulting (meth)acryl-basedpolymer (A) may be a random copolymer, a block copolymer, a graftcopolymer, or any other form.

In solution polymerization, for example, ethyl acetate, toluene, or thelike may be used as a polymerization solvent. An example of solutionpolymerization includes performing the reaction under a stream of inertgas such as nitrogen in the presence of a polymerization initiatortypically under the reaction conditions of a temperature of about 50 toabout 70° C. and a time period of about 5 to about 30 hours.

Any appropriately selected polymerization initiator, chain transferagent, emulsifier, or other agents may be used for radicalpolymerization. The weight average molecular weight of the(meth)acryl-based polymer (A) can be adjusted by controlling the amountof the polymerization initiator or the chain transfer agent or bycontrolling the reaction conditions. The amount of these agents may beadjusted as appropriate depending on the type of these agents.

Examples of the polymerization initiator include, but are not limitedto, azo initiators such as 2,2′-azobisisobutyronitrile,2,2′-azobis(2-amidinopropane)dihydrochloride,2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride,2,2′-azobis(2-methylpropionamidine)disulfate,2,2′-azobis(N,N′-dimethyleneisobutylamidine), and2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydra to (VA-057manufactured by Wako Pure Chemical Industries, Ltd.); persulfates suchas potassium persulfate and ammonium persulfate; peroxide initiatorssuch as di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl)peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butylperoxyneodecanoate, tert-hexyl peroxypivalate, tert-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide,1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, tert-butyl peroxyisobutyrate,1,1-di(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide, andhydrogen peroxide; and a redox system initiator including a combinationof a peroxide and a reducing agent, such as a combination of apersulfate and sodium hydrogen sulfite or a combination of a peroxideand sodium ascorbate.

The polymerization initiators may be used alone or in combination of twoor more. The total content of the polymerization initiator(s) ispreferably from about 0.005 to about 1 part by weight, more preferablyfrom about 0.02 to about 0.5 parts by weight, based on 100 parts byweight of the monomers.

For example, when the (meth)acryl-based polymer (A) with a weightaverage molecular weight as shown above is produced using2,2′-azobisisobutyronitrile as a polymerization initiator, the amount ofthe polymerization initiator is preferably from about 0.06 to about 0.2parts by weight, more preferably from about 0.08 to about 0.175 parts byweight, based on 100 parts by weight of all the monomers.

Examples of the chain transfer agent include lauryl mercaptan, glycidylmercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid,2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chaintransfer agents may be used alone or in combination of two or more. Thetotal content of the chain transfer agent (s) should be about 0.1 partsby weight or less based on 100 parts by weight of all the monomers.

Examples of the emulsifier for use in emulsion polymerization includeanionic emulsifiers such as sodium lauryl sulfate, ammonium laurylsulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkylether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate;and nonionic emulsifiers such as polyoxyethylene alkyl ether,polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester,and polyoxyethylene-polyoxypropylene block polymers. These emulsifiersmay be used alone or in combination of two or more.

The emulsifier may be a reactive emulsifier. Examples of such anemulsifier having an introduced radically-polymerizable functionalgroup, such as a propenyl group or an allyl ether group, include AQUALONHS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (all manufactured byDAI-ICHI KOGYO SEIYAKU CO., LTD.) and ADEKA REASOAP SE10N (manufacturedby ADEKA CORPORATION). The reactive emulsifier is preferred becauseafter polymerization, it can improve water resistance by beingincorporated in the polymer chain. Based on 100 parts by weight of allthe monomers, the emulsifier is preferably used in an amount of 0.3 to 5parts by weight, more preferably 0.5 to 1 part by weight, in view ofpolymerization stability or mechanical stability.

In addition to the (meth)acryl-based polymer (A), the pressure-sensitiveadhesive composition according to the present invention contains ioniccompounds each having an anion component and a cation component. Thepresent invention is particularly characterized in that two types ofionic compounds (B1) and (B2) are used in combination.

(Anion Component of the Ionic Compound (B1))

The anion component of the ionic compound (B1) has an organic group ofthree or more carbon atoms. When the ionic compound (B1) is used incombination with the (meth)acryl-based polymer (A), (i) an antistaticfunction can be imparted to the pressure-sensitive adhesive while areduction in the durability of the pressure-sensitive adhesive issignificantly suppressed, and (iii) an increase in surface resistanceafter humidification can be suppressed.

In particular, the anion component is preferably at least one of ananion component represented by formula (1):(C_(n)F_(2n+1)SO₂)₂N⁻  (1)

in formula (1), n is an integer of 3 to 10, an anion componentrepresented by formula (2):CF₂(C_(m)F_(2m)SO₂)₂N⁻  (2)

in formula (2), m is an integer of 2 to 10, an anion componentrepresented by formula (3):⁻O₃S(CF₂)_(l)SO₃ ⁻  (3)

in formula (3), l is an integer of 3 to 10, and an anion componentrepresented by formula (4):(C_(p)F_(2p+1)SO₂)N⁻(C_(q)F_(2q+1)SO₂)  (4)

in formula (4), p and q are each an integer of 2 to 10. This is becausewhen the anion component is at least one of them, the durability (i) andthe effect of suppressing an increase in surface resistance afterhumidification can be significantly increased.

For example, the anion component represented by formula (1) may be abis(heptafluoropropanesulfonyl) imide anion, abis(nonafluorobutanesulfonyl) imide anion, abis(undecafluoropentanesulfonyl)imide anion, abis(tridecafluorohexanesulfonyl)imide anion, or abis(pentadecafluoroheptanesulfonyl)imide anion. Among them, abis(heptafluoropropanesulfonyl)imide anion or abis(nanofluorobutanesulfonyl)imide anion is particularly preferred.

For example, the anion component represented by formula (2) may be acyclo-hexafluoropropane-1,3-bis(sulfonyl)imide anion, which can beadvantageously used.

For example, the anion component represented by formula (3) may be ahexafluoropropane-1,3-disulfonic acid anion, which can be advantageouslyused.

For example, the anion component represented by formula (4) may be atrifluoromethanesulfonylnonafluorobutanesulfonylimide anion, aheptafluoropropanesulfonyltrifluoromethanesulfonylimide anion, or apentafluoroethanesulfonylnonafluorobutanesulfonylimide anion, which canbe advantageously used.

(Anion Component of the Ionic Compound (B2))

The anion component of the ionic compound (B2) has an organic group oftwo or less carbon atoms. In this case, when the ionic compound (B2) isused in combination with the (meth)acryl-based polymer (A), (i) anantistatic function can be imparted to the pressure-sensitive adhesivewhile a reduction in the durability of the pressure-sensitive adhesiveis significantly suppressed, and (ii) the initial surface resistance canbe particularly reduced.

For example, the anion component having an organic group of two or lesscarbon atoms may be a bis(trifluoromethanesulfonyl)imide anion, atrifluoromethanesulfonyl anion, or a pentafluoroethanesulfonyl anion,which can be advantageously used.

(Cation Component of the Ionic Compounds)

The cation component of each of the ionic compounds including the ioniccompounds (B1) and (B2) may be any alkali metal ion such as a lithium,sodium, or potassium ion, which forms an alkali metal salt as the ioniccompound with the anion component shown above. When thepressure-sensitive adhesive composition contains an ionic compoundcontaining a potassium ion, among alkali metal ions, thepressure-sensitive adhesive layer made from the pressure-sensitiveadhesive composition tends to have a higher initial surface resistance.On the other hand, when the composition contains the ionic compound (B)containing a lithium ion, the initial surface resistance of thepressure-sensitive adhesive layer can be reduced (ii), and an increasein the surface resistance after humidification can be suppressed.

Generally, as the content of an ionic compound in a pressure-sensitiveadhesive composition increases, the antistatic performance of thecomposition increases, but the durability of the composition tends to beinsufficient. Generally, there tends to be a trade-off between theantistatic performance and the durability. However, when the ioniccompound (B) used contains a lithium ion, the antistatic performance,and particularly (iii) the moisture durability of the antistaticperformance can be improved even at a lower content of the ioniccompound (B). Therefore, the cation component of at least one of theionic compounds (B1) and (B2) is preferably a lithium cation.

Examples of the ionic compound (B1) as an alkali metal salt includelithium bis(heptafluoropropanesulfonyl)imide, sodiumbis(heptafluoropropanesulfonyl)imide, potassiumbis(heptafluoropropanesulfonyl)imide, lithiumbis(nonafluorobutanesulfonyl)imide, sodiumbis(nonafluorobutanesulfonyl)imide, potassiumbis(nonafluorobutanesulfonyl)imide, lithiumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide, sodiumcylco-hexafluoropropane-1,3-bis(sulfonyl)imide, potassiumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide,1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid dilithium salt,1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid disodium salt,1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid dipotassium salt,lithium bis(trifluoromethanesulfonyl)imide, sodiumbis(trifluoromethanesulfonyl)imide, potassiumbis(trifluoromethanesulfonyl)imide, lithiumtrifluoromethanesulfonylnonafluorobutanesulfonylimide, sodiumtrifluoromethanesulfonylnonafluorobutanesulfonylimide, potassiumtrifluoromethanesulfonylnonafluorobutanesulfonylimide, lithiumheptafluoropropanesulfonyltrifluoromethanesulfonylimide, sodiumheptafluoropropanesulfonyltrifluoromethanesulfonylimide, potassiumheptafluoropropanesulfonyltrifluoromethanesulfonylimide, lithiumpentafluoroethanesulfonylnonafluorobutanesulfonylimide, sodiumpentafluoroethanesulfonylnonafluorobutanesulfonylimide, and potassiumpentafluoroethanesulfonylnonafluorobutanesulfonylimide. Particularlypreferred are lithium bis(heptafluoropropanesulfonyl)imide, lithiumbis(nonafluorobutanesulfonyl)imide, lithiumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide,1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid dilithium salt,lithium trifluoromethanesulfonylnonafluorobutanesulfonylimide, lithiumheptafluoropropanesulfonyltrifluoromethanesulfonylimide, and lithiumpentafluoroethanesulfonylnonafluorobutanesulfonylimide.

Examples of the ionic compound (B2) as an alkali metal salt includelithium bis(trifluoromethanesulfonyl)imide, sodiumbis(trifluoromethanesulfonyl)imide, potassiumbis(trifluoromethanesulfonyl)imide, trifluoromethanesulfonyl lithium,trifluoromethanesulfonyl sodium, trifluoromethanesulfonyl potassium,pentafluoroethanesulfonyl lithium, pentafluoroethanesulfonyl sodium, andpentafluoroethanesulfonyl potassium.

The cation component of the ionic compound may also be an organiccation, which forms, together with the anion component, an organiccation-anion salt as the ionic compound. The organic cation-anion saltalso refers to as an ionic liquid or an ionic solid. Examples of theorganic cation include a pyridinium cation, a piperidinium cation, apyrrolidinium cation, a pyrroline skeleton-containing cation, a pyrroleskeleton-containing cation, an imidazolium cation, atetrahydropyrimidinium cation, a dihydropyrimidinium cation, apyrazolium cation, a pyrazolinium cation, a tetraalkylammonium cation, atrialkylsulfonium cation, and a tetraalkylphosphonium cation.

Compounds composed of combinations of any of the above cation componentsand any of the above anion components may be appropriately selected andused as examples of the organic cation-anion salt. Such examples of theionic compound (B1) include 1-butyl-3-methylpyridiniumbis(heptafluoropropanesulfonyl)imide, 1-butyl-3-methylpyridiniumbis(nonafluorobutanesulfonyl)imide, 1-butyl-3-methylpyridiniumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide,1-butyl-3-methylpyridiniumtrifluoromethanesulfonylnonafluorobutanesulfonylimide,1-butyl-3-methylpyridiniumheptafluoropropanesulfonyltrifluoromethanesulfonylimide,1-butyl-3-methylpyridiniumpentafluoroethanesulfonylnonafluorobutanesulfonylimide,1-ethyl-3-methylimidazolium bis(heptafluoropropanesulfonyl)imide,1-ethyl-3-methylimidazolium bis(nonafluorobutanesulfonyl)imide,1-ethyl-3-methylimidazoliumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide,1-ethyl-3-methylimidazoliumtrifluoromethanesulfonylnonafluorobutanesulfonylimide,1-ethyl-3-methylimidazoliumheptafluoropropanesulfonyltrifluoromethanesulfonylimide, and1-ethyl-3-methylimidazoliumpentafluoroethanesulfonylnonafluorobutanesulfonylimide. Such examples ofthe ionic compound (B2) include 1-butyl-3-methylpyridiniumbis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylpyridiniumbis(pentafluoroethanesulfonyl)imide, 1-ethyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide, and 1-ethyl-3-methylimidazoliumbis(pentafluoroethanesulfonyl)imide.

The contents of the ionic compounds (B1) and (B2) in thepressure-sensitive adhesive composition of the present invention areeach preferably from 0.001 to 4 parts by weight based on 100 parts byweight of the (meth)acryl-based polymer (A). If the contents of theionic compounds (B1) and (B2) are each less than 0.001 part by weight,one of the effect (i) of reducing the initial surface resistance and theeffect (iii) of improving the moisture durability of the antistaticfunction may be insufficient. The contents of the ionic compounds (B1)and (B2) are each preferably 0.01 parts by weight or more, morepreferably 0.1 parts by weight or more. If the contents of the ioniccompounds (B1) and (B2) are each more than 4 parts by weight, thedurability (i) may be insufficient. The contents of these compounds areeach preferably 2 parts by weight or less, more preferably 1 part byweight or less. The preferred range of the contents of the ioniccompounds (B1) and (B2) may determined based on the above upper andlower limit values.

The content ratio of the ionic compound (B1) to the ionic compound (B2)is preferably from 1:5 to 5:1, more preferably from 1:2 to 2:1, so thatthe effect (i) of reducing the initial surface resistance and the effect(iii) of improving the moisture durability of the antistatic functioncan be further increased in a well-balanced manner.

The pressure-sensitive adhesive composition of the present invention mayfurther contain (C) a crosslinking agent. The crosslinking agent (C) maybe an organic crosslinking agent or a polyfunctional metal chelate.Examples of the organic crosslinking agent include an isocyanatecrosslinking agent, a peroxide crosslinking agent, an epoxy crosslinkingagent, an imine crosslinking agent, or the like. The polyfunctionalmetal chelate is a compound containing a polyvalent metal covalently orcoordinately bonded to an organic compound. Examples of the polyvalentmetal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y,Ce, Sr, Ba, Mo, La, Sn, Ti, or the like. The organic compound has acovalent or coordinate bond-forming atom such as an oxygen atom.Examples of the organic compound include an alkyl ester, an alcoholcompound, a carboxylic acid compound, an ether compound, and a ketonecompound.

The crosslinking agent (C) is preferably an isocyanate crosslinkingagent and/or a peroxide crosslinking agent. Examples of compounds foruse as isocyanate crosslinking agents include isocyanate monomers suchas tolylene diisocyanate, chlorophenylene diisocyanate, tetramethylenediisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, andhydrogenated diphenylmethane diisocyanate, and isocyanate, isocyanurate,or biuret compounds produced by adding any of these isocyanate monomersto trimethylolpropane or other compounds; and urethane prepolymer typeisocyanates produced by addition reaction of any of these isocyanatecompounds with polyether polyols, polyester polyols, acrylic polyols,polybutadiene polyols, polyisoprenepolyols, or other polyols.Particularly preferred is a polyisocyanate compound such as one selectedfrom the group consisting of hexamethylene diisocyanate, hydrogenatedxylylene diisocyanate, and isophorone diisocyanate, or a derivativethereof. Examples of one selected from the group consisting ofhexamethylene diisocyanate, hydrogenated xylylene diisocyanate, andisophorone diisocyanate, or a derivative thereof include hexamethylenediisocyanate, hydrogenated xylylene diisocyanate, isophoronediisocyanate, polyol-modified hexamethylene diisocyanate,polyol-modified hydrogenated xylylene diisocyanate, trimer-typehydrogenated xylylene diisocyanate, and polyol-modified isophoronediisocyanate. The listed polyisocyanate compounds are preferred becausetheir reaction with a hydroxyl group quickly proceeds as if an acid or abase contained in the polymer acts as a catalyst, which particularlycontributes to the rapidness of the crosslinking.

Any peroxide capable of generating active radical species upon heatingor exposure to light and capable of crosslinking the base polymer in thepressure-sensitive adhesive composition can be used appropriately. Inview of workability or stability, a peroxide with a one-minute half-lifetemperature of 80° C. to 160° C. is preferably used, and a peroxide witha one-minute half-life temperature of 90° C. to 140° C. is morepreferably used.

Examples of peroxides that may be used include di(2-ethylhexyl)peroxydicarbonate (one-minute half-life temperature: 90.6° C.),di(4-tert-butylcyclohexyl) peroxydicarbonate (one-minute half-lifetemperature: 92.1° C.), di-sec-butyl peroxydicarbonate (one-minutehalf-life temperature: 92.4° C.), tert-butyl peroxyneodecanoate(one-minute half-life temperature: 103.5° C.), tert-hexyl peroxypivalate(one-minute half-life temperature: 109.1° C.), tert-butyl peroxypivalate(one-minute half-life temperature: 110.3° C.), dilauroyl peroxide(one-minute half-life temperature: 116.4° C.), di-n-octanoyl peroxide(one-minute half-life temperature: 117.4° C.),1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate (one-minute half-lifetemperature: 124.3° C.), di(4-methylbenzoyl) peroxide (one-minutehalf-life temperature: 128.2° C.), dibenzoyl peroxide (one-minutehalf-life temperature: 130.0° C.), tert-butyl peroxyisobutyrate(one-minute half-life temperature: 136.1° C.), and1,1-di(tert-hexylperoxy)cyclohexane (one-minute half-life temperature:149.2° C.). In particular, di(4-tert-butylcyclohexyl) peroxydicarbonate(one-minute half-life temperature: 92.1° C.), dilauroyl peroxide(one-minute half-life temperature: 116.4° C.), and dibenzoyl peroxide(one-minute half-life temperature: 130.0° C.) are preferably usedbecause they can provide higher crosslinking reaction efficiency.

The half life of a peroxide, which is an indicator of how fast theperoxide can be decomposed, refers to the time required for theremaining amount of the peroxide to reach one half of the originalamount. The decomposition temperature required for a certain half lifetime and the half life time obtained at a certain temperature are shownin catalogs furnished by manufacturers, such as Organic PeroxideCatalog, 9th Edition, May 2003, furnished by NOF CORPORATION.

The crosslinking agent (C) is preferably used in an amount of 0.01 to 20parts by weight, more preferably 0.03 to 10 parts by weight, based on100 parts by weight of the (meth)acryl-based polymer (A). If the amountof the crosslinking agent (C) is less than 0.01 part by weight, thepressure-sensitive adhesive may tend to have insufficient cohesivestrength, and foaming may occur during the heating of the composition.On the other hand, if it is more than 20 parts by weight, thepressure-sensitive adhesive may have insufficient moisture resistanceand may easily peel off in a reliability test or the like.

The above isocyanate crosslinking agents may be used alone or in amixture of two or more. The total content of the isocyanate crosslinkingagent(s) is preferably from 0.01 to 2 parts by weight, more preferablyfrom 0.02 to 2 parts by weight, even more preferably from 0.05 to 1.5parts by weight, based on 100 parts by weight of the (meth)acryl-basedpolymer (A). The content may be appropriately determined taking intoaccount cohesive strength, the ability to prevent delamination in adurability test, or other properties.

The above peroxides may be used alone or in a mixture of two or more.The total content of the peroxide (s) is preferably from 0.01 to 2 partsby weight, more preferably from 0.04 to 1.5 parts by weight, even morepreferably from 0.05 to 1 part by weight, based on 100 parts by weightof the (meth)acryl-based polymer (A). The content may be appropriatelyselected in these ranges for control of workability, reworkability,crosslinking stability, peeling properties, or other properties.

For example, the amount of decomposition of the peroxide can bedetermined by a method of measuring the peroxide residue after thereaction process by high performance liquid chromatography (HPLC).

More specifically, for example, after the reaction process, about 0.2 gof each pressure-sensitive adhesive composition is taken out andimmersed in 10 ml of ethyl acetate and subjected to shaking extractionat 25° C. and 120 rpm for 3 hours in a shaker, and then allowed to standat room temperature for 3 days. Subsequently, 10 ml of acetonitrile isadded, and the mixture is shaken at 25° C. and 120 rpm for 30 minutes.About 10 μl of the liquid extract obtained by filtration through amembrane filter (0.45 μm) is subjected to HPLC by injection and analyzedso that the amount of the peroxide after the reaction process isdetermined.

The pressure-sensitive adhesive composition of the present invention mayfurther contain a silane coupling agent (D). Durability can be improvedusing the silane coupling agent (D). Examples of the silane couplingagent include epoxy group-containing silane coupling agents such as3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,3-glycidoxypropylmethyldiethoxysilane, and2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containingsilane coupling agents such as 3-aminopropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, andN-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containingsilane coupling agents such as 3-acryloxypropyltrimethoxysilane and3-methacryloxypropyltriethoxysilane; and isocyanate group-containingsilane coupling agents such as 3-isocyanatopropyltriethoxysilane.

The silane coupling agent (D) may have an acetoacetyl group and areactive silyl group represented by formula (3): —SiR_(a)M_(3-a),wherein R is a monovalent organic group having 1 to 20 carbon atoms andoptionally having a substituent, M is a hydroxyl group or a hydrolyzablegroup, and a is an integer of 0 to 2. In the formula, two or more Rgroups, if any, may be the same or different, and two or more M groups,if any, may be the same or different. The silane coupling agent (D)having both a reactive silyl group and an acetoacetyl group may be acommercially available product such as A100 manufactured by SokenChemical & Engineering Co., Ltd.

The above compounds for the silane coupling agent (D) may be used aloneor in a mixture of two or more. The total content of the silane couplingagent(s) is preferably from 0.001 to 5 parts by weight, more preferablyfrom 0.01 to 1 part by weight, even more preferably from 0.02 to 1 partby weight, furthermore preferably from 0.05 to 0.6 parts by weight,based on 100 parts by weight of the (meth)acryl-based polymer (A). Usingsuch an amount of the silane coupling agent, durability can be improved,and the adhering strength to an optical member such as a liquid crystalcell can be kept at an appropriate level.

The pressure-sensitive adhesive composition of the present invention mayfurther contain a polyether-modified silicone (E). For example, thecompound disclosed in JP-A-2010-275522 may be used as thepolyether-modified silicone (E).

The polyether-modified silicone (E) may have a polyether skeleton and areactive silyl group at least one end, wherein the reactive silyl groupis represented by formula (3): —SiR_(a)M_(3-a), wherein R is amonovalent organic group having 1 to 20 carbon atoms and optionallyhaving a substituent, M is a hydroxyl group or a hydrolyzable group, anda is an integer of 0 to 2. In the formula, two or more R groups, if any,may be the same or different, and two or more M groups, if any, may bethe same or different. When the pressure-sensitive adhesive layer of thepressure-sensitive adhesive layer-bearing optical film contains thepolyether-modified silicone (E), the adhering strength of thepressure-sensitive adhesive-bearing optical film bonded to a liquidcrystal cell or other components can be properly kept from increasingeven after storage at high temperature or after various processes areperformed over a long time. In this case, the pressure-sensitiveadhesive layer-bearing optical film has high reworkability and can beeasily peeled off from the liquid crystal cell or other components, sothat the liquid crystal cell can be reused without damage or pollution.In particular, it has been difficult to peel off conventionalpressure-sensitive adhesive layer-bearing optical films from largeliquid crystal cells. According to the present invention, however, thepressure-sensitive adhesive layer-bearing optical film can be easilypeeled off even from a large liquid crystal cell.

The polyether-modified silicone (E) may be a compound represented byformula (5): R_(a)M_(3-a)Si—X—Y-(AO)_(n)—Z, wherein R is a monovalentorganic group having 1 to 20 carbon atoms and optionally having asubstituent, M is a hydroxyl group or a hydrolyzable group, and a is aninteger of 0 to 2. In the formula, two or more R groups, if any, may bethe same or different, and two or more M groups, if any, may be the sameor different. AO is a straight- or branched-chain oxyalkylene group of 1to 10 carbon atoms, and n is the average number of moles of the addedoxyalkylene group and is from 1 to 1,700. X is a straight- orbranched-chain alkylene group of 1 to 20 carbon atoms. Y is an etherbond, an ester bond, a urethane bond, or a carbonate bond.

Z is a hydrogen atom, a monovalent hydrocarbon group of 1 to 10 carbonatoms,

a group represented by formula (4A): —Y₁—X—SiR_(a)M_(3-a), wherein R, M,X, and a have the same meanings as defined above, and Y₁ is a singlebond, a —CO— bond, a —CONH— bond, or a —COO— bond, or

a group represented by formula (4B):

-Q{-(OA)_(n)-Y—X—SiR_(a)M_(3-a)}_(m), wherein R, M, X, Y, and a have thesame meanings as defined above, OA has the same meaning as AO definedabove, n has the same meaning as defined above, Q is a divalent orpolyvalent hydrocarbon group of 1 to 10 carbon atoms, and m is a numberthat is the same as the valence of the hydrocarbon group.

Examples of the polyether-modified silicone (E) include MS Polymers5203, 5303, and 5810 manufactured by Kaneka Corporation; SILYL EST250and EST280 manufactured by Kaneka Corporation; SILYL SAT10, SILYLSAT200, SILYL SAT220, SILYL SAT350, and SILYL SAT400 manufactured byKaneka Corporation; and EXCESTAR 52410, 52420, or 53430 manufacture byASAHI GLASS CO., LTD.

The pressure-sensitive adhesive composition of the present invention mayfurther contain any other known additive such as a powder of a colorant,a pigment, or the like, a dye, a surfactant, a plasticizer, a tackifier,a surface lubricant, a leveling agent, a softening agent, anantioxidant, an age resistor, a light stabilizer, an ultravioletabsorber, a polymerization inhibitor, an inorganic or organic filler, ametal powder, or a particulate or flaky material, which may be added asappropriate depending on the intended use. Within the controllablerange, a reducing agent may also be added to form a redox system.

When the pressure-sensitive adhesive composition is used to form apressure-sensitive adhesive layer, it is preferred that the totalcontent of the crosslinking agent should be controlled and that theeffect of the crosslinking temperature or the crosslinking time shouldbe carefully taken into account.

The crosslinking temperature and the crosslinking time may be controlleddepending on the type of the crosslinking agent to be used. Thecrosslinking temperature is preferably 170° C. or lower.

The crosslinking process may be performed at the temperature where theprocess of drying the pressure-sensitive adhesive layer is performed, oran independent crosslinking process may be performed after the dryingprocess.

The crosslinking time may be determined in view of productivity orworkability. The crosslinking time is generally from about 0.2 to about20 minutes, preferably from about 0.5 to about 10 minutes.

The pressure-sensitive adhesive layer-bearing polarizing film of thepresent invention includes a polarizing film and a pressure-sensitiveadhesive layer formed on at least one side of the polarizing film andmade from the pressure-sensitive adhesive composition.

For example, the pressure-sensitive adhesive layer can be formed by amethod including applying the pressure-sensitive adhesive composition toa release-treated separator or the like, removing the polymerizationsolvent and so on from the composition by drying to form apressure-sensitive adhesive layer, and then transferring thepressure-sensitive adhesive layer onto a polarizing film. Alternatively,the pressure-sensitive adhesive layer can be formed by a methodincluding applying the pressure-sensitive adhesive composition to apolarizing film and removing the polymerization solvent and so on fromthe composition by drying to form a pressure-sensitive adhesive layer onthe polarizing film. In the process of applying the pressure-sensitiveadhesive, if necessary, one or more solvents other than thepolymerization solvent may be newly added to the composition.

A silicone release liner is preferably used as the release-treatedseparator. The adhesive composition of the present invention may beapplied to such a liner and dried to form a pressure-sensitive adhesivelayer. In this process, any appropriate method may be used for dryingthe pressure-sensitive adhesive, depending on the purpose. Preferably, amethod of heating and drying the coating is used. The heating and dryingtemperature is preferably from 40° C. to 200° C., more preferably from50° C. to 180° C., even more preferably from 70° C. to 170° C. When theheating temperature falls within the range, a pressure-sensitiveadhesive with a high level of adhesive properties can be obtained.

The drying may be performed for any appropriate time. The drying time ispreferably from 5 seconds to 20 minutes, more preferably from 5 secondsto 10 minutes, even more preferably from 10 seconds to 5 minutes.

An anchor layer may also be formed on the surface of the polarizingfilm, or an adhesion-facilitating layer may also be formed on thesurface of the polarizing film by any of various adhesion-facilitatingtreatments such as a corona treatment and a plasma treatment, and thepressure-sensitive adhesive layer may be formed on the anchor layer orthe adhesion-facilitating layer. The surface of the pressure-sensitiveadhesive layer may also be subjected to an adhesion-facilitatingtreatment.

Various methods may be used to form the pressure-sensitive adhesivelayer. Examples of such methods include roll coating, kiss roll coating,gravure coating, reverse coating, roll brush coating, spray coating, diproll coating, bar coating, knife coating, air knife coating, curtaincoating, lip coating, and extrusion coating with a die coater or thelike.

The thickness of the pressure-sensitive adhesive layer is typically, butnot limited to, about 1 to about 100 μm, preferably 2 to 50 μm, morepreferably 2 to 40 μm, even more preferably 5 to 35 μm.

When the surface of the pressure-sensitive adhesive layer is exposed,the pressure-sensitive adhesive layer may be protected by arelease-treated sheet (separator) until it is actually used.

Examples of the material used to form such a separator include a plasticfilm such as a polyethylene, polypropylene, polyethylene terephthalate,or polyester film, a porous material such as paper, cloth, or nonwovenfabric, and appropriate thin materials such as a net, a foamed sheet, ametal foil, and a laminate thereof. Aplastic film is advantageously usedbecause of its good surface smoothness.

Such a plastic film may be of any type capable of protecting thepressure-sensitive adhesive layer. For example, such a plastic film maybe a polyethylene film, a polypropylene film, a polybutene film, apolybutadiene film, a polymethylpentene film, a polyvinyl chloride film,a vinyl chloride copolymer film, a polyethylene terephthalate film, apolybutylene terephthalate film, a polyurethane film, or anethylene-vinyl acetate copolymer film.

The separator generally has a thickness of about 5 to about 200 μm,preferably about 5 to about 100 μm. If necessary, the separator may besubjected to a release treatment and an anti-pollution treatment with asilicone, fluoride, long-chain alkyl, or fatty acid amide release agent,a silica powder or the like, or subjected to an antistatic treatment ofcoating type, kneading and mixing type, vapor-deposition type, or thelike. In particular, when the surface of the separator is appropriatelysubjected to a release treatment such as a silicone treatment, along-chain alkyl treatment, or a fluorine treatment, the releasabilityfrom the pressure-sensitive adhesive layer can be further improved.

The release-treated sheet used in the preparation of thepressure-sensitive adhesive layer-bearing polarizing film may be used byitself as a separator for the pressure-sensitive adhesive layer-bearingpolarizing film, so that the process can be simplified.

The pressure-sensitive adhesive layer-bearing polarizing film accordingto the present invention includes at least a polarizing film and thepressure-sensitive adhesive layer described above. The polarizing filmused generally includes a polarizer and a transparent protective film orfilms provided on one or both sides of the polarizer.

Any of various polarizers may be used without restriction. For example,the polarizer may be a product produced by a process including adsorbinga dichroic material such as iodine or a dichroic dye to a hydrophilicpolymer film such as a polyvinyl alcohol-based film, apartially-formalized polyvinyl alcohol-based film, or apartially-saponified, ethylene-vinyl acetate copolymer-based film anduniaxially stretching the film or may be a polyene-based oriented filmsuch as a film of a dehydration product of polyvinyl alcohol or adehydrochlorination product of polyvinyl chloride. In particular, apolarizer including a polyvinyl alcohol-based film and a dichroicmaterial such as iodine is advantageous. The thickness of the polarizeris generally, but not limited to, about 80 μm or less.

For example, a polarizer including a uniaxially-stretched polyvinylalcohol-based film dyed with iodine can be produced by a processincluding immersing a polyvinyl alcohol film in an aqueous iodinesolution to dye the film and stretching the film to 3 to 7 times theoriginal length. If necessary, the film may also be immersed in anaqueous solution of potassium iodide or the like optionally containingboric acid, zinc sulfate, zinc chloride, or other materials. Ifnecessary, the polyvinyl alcohol-based film may be further immersed inwater for washing before it is dyed. If the polyvinyl alcohol-based filmis washed with water, dirt and any anti-blocking agent can be cleanedfrom the surface of the polyvinyl alcohol-based film, and the polyvinylalcohol-based film can also be allowed to swell so that unevenness suchas uneven dyeing can be effectively prevented. The film may be stretchedbefore, while, or after it is dyed with iodine. The film may also bestretched in an aqueous solution of boric acid, potassium iodide, or thelike or in a water bath.

A thin polarizer with a thickness of 10 μm or less may also be used. Inview of thickness reduction, the thickness is preferably from 1 to 7 μm.Such a thin polarizer is less uneven in thickness, has good visibility,and is less dimensionally-variable, and thus has high durability. It isalso preferred because it can form a thinner polarizing film.

Typical examples of such a thin polarizer include the thin polarizingfilms (polarizers) described in JP-A-51-069644, JP-A-2000-338329,WO2010/100917, PCT/JP2010/001460, Japanese Patent Application No.2010-269002, and Japanese Patent Application No. 2010-263692. These thinpolarizing films can be obtained by a process including the steps ofstretching a laminate of a polyvinyl alcohol-based resin (hereinafteralso referred to as PVA-based resin) layer and a stretchable resinsubstrate and dyeing the laminate. Using this process, the PVA-basedresin layer, even when thin, can be stretched without problems such asbreakage by stretching, because the layer is supported on thestretchable resin substrate.

Among processes including the steps of stretching and dyeing a laminate,a process capable of achieving high-ratio stretching to improvepolarizing performance is preferably used when the thin polarizing filmis formed. Thus, the thin polarizing film is preferably obtained by aprocess including the step of stretching in an aqueous boric acidsolution as described in WO2010/100917, PCT/JP2010/001460, JapanesePatent Application No. 2010-269002, or Japanese Patent Application No.2010-263692, and more preferably obtained by a process including thestep of performing auxiliary in-air stretching before stretching in anaqueous boric acid solution as described in Japanese Patent ApplicationNo. 2010-269002 or 2010-263692.

PCT/JP2010/001460 describes a thin highly-functional polarizing filmthat is formed integrally with a resin substrate, made of a PVA-basedresin containing an oriented dichroic material, and has a thickness of 7μm or less and the optical properties of a single transmittance of 42.0%or more and a degree of polarization of 99.95% or more.

This thin highly-functional polarizing film can be produced by a processincluding forming a PVA-based resin coating on a resin substrate with athickness of at least 20 μm, drying the coating to form a PVA-basedresin layer, immersing the resulting PVA-based resin layer in a dyeingliquid containing a dichroic material to adsorb the dichroic material tothe PVA-based resin layer, and stretching the PVA-based resin layer,which contains the adsorbed dichroic material, together with the resinsubstrate in an aqueous boric acid solution to a total stretch ratio of5 times or more the original length.

A laminated film including a thin highly-functional polarizing filmcontaining an oriented dichroic material can also be produced by amethod including the steps of: applying a PVA-based resin-containingaqueous solution to one side of a resin substrate with a thickness of atleast 20 μm, drying the coating to form a PVA-based resin layer so thata laminated film including the resin substrate and the PVA-based resinlayer formed thereon is produced; immersing the laminated film in adyeing liquid containing a dichroic material to adsorb the dichroicmaterial to the PVA-based resin layer in the laminated film, wherein thelaminated film includes the resin substrate and the PVA-based resinlayer formed on one side of the resin substrate; and stretching thelaminated film, which has the PVA-based resin layer containing theadsorbed dichroic material, in an aqueous boric acid solution to a totalstretch ratio of 5 times or more the original length, wherein thePVA-based resin layer containing the adsorbed dichroic material isstretched together with the resin substrate, so that a laminated filmincluding the resin substrate and a thin highly-functional polarizingfilm formed on one side of the resin substrate is produced, in which thethin highly-functional polarizing film is made of the PVA-based resinlayer containing the oriented dichroic material and has a thickness of 7μm or less and the optical properties of a single transmittance of 42.0%or more and a degree of polarization of 99.95% or more.

In the present invention, the polarizer with a thickness of 10 μm orless used to form the pressure-sensitive adhesive layer-bearingpolarizing film may be a polarizing film in the form of a continuous webincluding a PVA-based resin containing an oriented dichroic material.Such a polarizing film can be obtained by a two-stage stretching processincluding auxiliary in-air stretching of a laminate including athermoplastic resin substrate and a polyvinyl alcohol-based resin layerformed thereon and stretching of the laminate in an aqueous boric acidsolution. The thermoplastic resin substrate is preferably an amorphouspolyester-based thermoplastic resin substrate or a crystallinepolyester-based thermoplastic resin substrate.

The thin polarizing film disclosed in Japanese Patent Application No.2010-269002 or 2010-263692 is a polarizing film in the form of acontinuous web including a PVA-based resin containing an orienteddichroic material, which is made with a thickness of 10 μm or less by atwo-stage stretching process including auxiliary in-air stretching of alaminate and stretching of the laminate in an aqueous boric acidsolution, wherein the laminate includes an amorphous polyester-basedthermoplastic resin substrate and a PVA-based resin layer formedthereon. This thin polarizing film is preferably made to have opticalproperties satisfying the following conditions:P>-(10^(0.929T-42.4)−1)×100 (provided that T<42.3) and P≧99.9 (providedthat T≧42.3), wherein T represents the single transmittance, and Prepresents the degree of polarization.

Specifically, the thin polarizing film can be produced by a thinpolarizing film-manufacturing method including the steps of: performingelevated temperature in-air stretching of a PVA-based resin layer formedon an amorphous polyester-based thermoplastic resin substrate in theform of a continuous web, so that a stretched intermediate productincluding an oriented PVA-based resin layer is produced; adsorbing adichroic material (which is preferably iodine or a mixture of iodine andan organic dye) to the stretched intermediate product to produce a dyedintermediate product including the PVA-based resin layer and thedichroic material oriented therein; and performing stretching of thedyed intermediate product in an aqueous boric acid solution so that apolarizing film with a thickness of 10 μm or less is produced, whichincludes the PVA-based resin layer and the dichroic material orientedtherein.

In this manufacturing method, the elevated temperature in-air stretchingand the stretching in an aqueous boric acid solution are preferablyperformed in such a manner that the PVA-based resin layer formed on theamorphous polyester-based thermoplastic resin substrate is stretched toa total stretch ratio of 5 times or more. The temperature of the aqueousboric acid solution for the stretching therein may be 60° C. or higher.Before stretched in the aqueous boric acid solution, the dyedintermediate product is preferably subjected to an insolubilizationtreatment, in which the dyed intermediate product is preferably immersedin an aqueous boric acid solution at a temperature of 40° C. or lower.The amorphous polyester-based thermoplastic resin substrate may be madeof amorphous polyethylene terephthalate including co-polyethyleneterephthalate in which isophthalic acid, cyclohexanedimethanol, or anyother monomer is copolymerized. The amorphous polyester-basedthermoplastic resin substrate is preferably made of a transparent resin.The thickness of the substrate may be at least 7 times the thickness ofthe PVA-based resin layer to be formed. The elevated temperature in-airstretching is preferably performed at a stretch ratio of 3.5 times orless. The temperature of the elevated temperature in-air stretching ispreferably equal to or higher than the glass transition temperature ofthe PVA-based resin. Specifically, it is preferably in the range of 95°C. to 150° C. When the elevated temperature in-air stretching isend-free uniaxial stretching, the PVA-based resin layer formed on theamorphous polyester-based thermoplastic resin substrate is preferablystretched to a total stretch ratio of 5 to 7.5 times. When the elevatedtemperature in-air stretching is fixed-end uniaxial stretching, thePVA-based resin layer formed on the amorphous polyester-basedthermoplastic resin substrate is preferably stretched to a total stretchratio of 5 to 8.5 times.

More specifically, the thin polarizing film can be produced by themethod described below.

A substrate is prepared in the form of a continuous web, which is madeof co-polyethylene terephthalate-isophthalate (amorphous PET) containing6 mol % of copolymerized isophthalic acid. The amorphous PET has a glasstransition temperature of 75° C. A laminate of a polyvinyl alcohol (PVA)layer and the amorphous PET substrate in the form of a continuous web isprepared as described below. For reference, the glass transitiontemperature of PVA is 80° C.

A 200-μm-thick amorphous PET substrate is provided, and an aqueous 4-5%PVA solution is prepared by dissolving a PVA powder with apolymerization degree of 1,000 or more and a saponification degree of99% or more in water. Subsequently, the aqueous PVA solution is appliedto the 200-μm-thick amorphous PET substrate and dried at a temperatureof 50 to 60° C. so that a laminate composed of the amorphous PETsubstrate and a 7-μm-thick PVA layer formed thereon is obtained.

The laminate having the 7-μm-thick PVA layer is subjected to a two-stagestretching process including auxiliary in-air stretching and stretchingin an aqueous boric acid solution as described below, so that a thinhighly-functional polarizing film with a thickness of 3 μm is obtained.At the first stage, the laminate having the 7-μm-thick PVA layer issubjected to an auxiliary in-air stretching step so that the layer isstretched together with the amorphous PET substrate to form a stretchedlaminate having a 5-μm-thick PVA layer. Specifically, the stretchedlaminate is formed by a process including feeding the laminate havingthe 7-μm-thick PVA layer to a stretching apparatus placed in an ovenwith the stretching temperature environment set at 130° C. andsubjecting the laminate to end-free uniaxial stretching to a stretchratio of 1.8 times. In the stretched laminate, the PVA layer ismodified, by the stretching, into a 5-μm-thick PVA layer containingoriented PVA molecules.

Subsequently, a dyeing step is performed to produce a dyed laminatehaving a 5-μm-thick PVA layer containing oriented PVA molecules andadsorbed iodine. Specifically, the dyed laminate is produced byimmersing the stretched laminate for a certain period of time in adyeing liquid containing iodine and potassium iodide and having atemperature of 30° C. so that iodine can be adsorbed to the PVA layer ofthe stretched laminate and so that the PVA layer for finally forming ahighly-functional polarizing film can have a single transmittance of 40to 44%. In this step, the dyeing liquid contains water as a solvent andiodine at a concentration in the range of 0.12 to 0.30% by weight, andpotassium iodide at a concentration in the range of 0.7 to 2.1% byweight. The concentration ratio of iodine to potassium iodide is 1:7. Itshould be noted that potassium iodide is necessary to make iodinesoluble in water. More specifically, the stretched laminate is immersedfor 60 seconds in a dyeing liquid containing 0.30% by weight of iodineand 2.1% by weight of potassium iodide, so that a dyed laminate isproduced, in which the 5-μm-thick PVA layer contains oriented PVAmolecules and adsorbed iodine.

At the second stage, the dyed laminate is further subjected to astretching step in an aqueous boric acid solution so that the layer isfurther stretched together with the amorphous PET substrate to form anoptical film laminate having a 3-μm-thick PVA layer, which forms ahighly-functional polarizing film. Specifically, the optical filmlaminate is formed by a process including feeding the dyed laminate to astretching apparatus placed in a treatment system where an aqueous boricacid solution containing boric acid and potassium iodide is set in thetemperature range of 60 to 85° C., and subjecting the laminate toend-free uniaxial stretching to a stretch ratio of 3.3 times. Morespecifically, the aqueous boric acid solution has a temperature of 65°C. In the solution, the boric acid content and the potassium iodidecontent are 4 parts by weight and 5 parts by weight, respectively, basedon 100 parts by weight of water. In this step, the dyed laminate havinga controlled amount of adsorbed iodine is first immersed in the aqueousboric acid solution for 5 to 10 seconds. Subsequently, the dyed laminateis directly fed between a plurality of pairs of rolls different inperipheral speed, which form the stretching apparatus placed in thetreatment system, and subjected to end-free uniaxial stretching for 30to 90 seconds to a stretch ratio of 3.3 times. This stretching treatmentconverts the PVA layer of the dyed laminate to a 3-μm-thick PVA layer inwhich the adsorbed iodine forms a polyiodide ion complex highly orientedin a single direction. This PVA layer forms a highly-functionalpolarizing film in the optical film laminate.

A cleaning step, although not essential for the manufacture of theoptical film laminate, is preferably performed, in which the opticalfilm laminate is taken out of the aqueous boric acid solution, and boricacid deposited on the surface of the 3-μm-thick PVA layer formed on theamorphous PET substrate is washed off with an aqueous potassium iodidesolution. Subsequently, the cleaned optical film laminate is dried in adrying step using warm air at 60° C. It should be noted that thecleaning step is to prevent appearance defects such as boric acidprecipitation.

A lamination and/or transfer step, although not essential for themanufacture of the optical film laminate, may also be performed, inwhich an 80-μm-thick triacetylcellulose film is bonded to the surface ofthe 3-μm-thick PVA layer on the amorphous PET substrate while anadhesive is applied to the surface, and then the amorphous PET substrateis peeled off, so that the 3-μm-thick PVA layer is transferred onto the80-μm-thick triacetylcellulose film.

[Other Steps]

The thin polarizing film-manufacturing method may include other steps inaddition to the above steps. For example, such other steps may includean insolubilization step, a crosslinking step, a drying step (moisturecontrol), etc. Other steps may be performed at any appropriate timing.

The insolubilization step is typically achieved by immersing thePVA-based resin layer in an aqueous boric acid solution. Theinsolubilization treatment can impart water resistance to the PVA-basedresin layer. The concentration of boric acid in the aqueous boric acidsolution is preferably from 1 to 4 parts by weight based on 100 parts byweight of water. The insolubilization bath (aqueous boric acid solution)preferably has a temperature of 20° C. to 50° C. Preferably, theinsolubilization step is performed after the preparation of the laminateand before the dyeing step or the step of stretching in water.

The crosslinking step is typically achieved by immersing the PVA-basedresin layer in an aqueous boric acid solution. The crosslinkingtreatment can impart water resistance to the PVA-based resin layer. Theconcentration of boric acid in the aqueous boric acid solution ispreferably from 1 to 4 parts by weight based on 100 parts by weight ofwater. When the crosslinking step is performed after the dyeing step, aniodide is preferably added to the solution. The addition of an iodidecan suppress the elution of adsorbed iodine from the PVA-based resinlayer. The amount of the addition of an iodide is preferably from 1 to 5parts by weight based on 100 parts by weight of water. Examples of theiodide include those listed above. The temperature of the crosslinkingbath (aqueous boric acid solution) is preferably from 20° C. to 50° C.Preferably, the crosslinking step is performed before the secondstretching step in the aqueous boric acid solution. In a preferredembodiment, the dyeing step, the crosslinking step, and the secondstretching step in the aqueous boric acid solution are performed in thisorder.

The material used to form the transparent protective film is typicallythermoplastic resin with a high level of transparency, mechanicalstrength, thermal stability, water blocking properties, isotropy, etc.Examples of such thermoplastic resin include cellulose resin such astriacetylcellulose, polyester resin, polyethersulfone resin, polysulfoneresin, polycarbonate resin, polyamide resin, polyimide resin, polyolefinresin, (meth)acrylic resin, cyclic polyolefin resin (norbornene resin),polyarylate resin, polystyrene resin, polyvinyl alcohol resin, and anyblend thereof. The transparent protective film may be bonded to one sideof the polarizer with an adhesive layer. In this case, thermosetting orultraviolet-curable resin such as (meth)acrylic, urethane, acrylicurethane, epoxy, or silicone resin may be used to form a transparentprotective film on the other side. The transparent protective film maycontain any one or more appropriate additives. Examples of such anadditive include an ultraviolet absorber, an antioxidant, a lubricant, aplasticizer, a release agent, an anti-discoloration agent, a flameretardant, a nucleating agent, an antistatic agent, a pigment, and acolorant. The content of the thermoplastic resin in the transparentprotective film is preferably from 50 to 100% by weight, more preferablyfrom 50 to 99% by weight, even more preferably from 60 to 98% by weight,further more preferably from 70 to 97% by weight. If the content of thethermoplastic resin in the transparent protective film is less than 50%by weight, high transparency and other properties inherent in thethermoplastic resin may be insufficiently exhibited.

The polarizer and the transparent protective film may be bonded togetherwith an adhesive. Examples of such an adhesive include isocyanateadhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives,vinyl adhesives, latex adhesives, and aqueous polyester adhesives. Theadhesive is generally used in the form of an aqueous adhesive solution,which generally has a solids content of 0.5 to 60% by weight. Besidesthe above, ultraviolet-curable adhesives, electron beam-curableadhesives, or the like may also be used to bond the polarizer and thetransparent protective film together. Electron beam-curable adhesivesfor use on polarizing films have good tackiness to the varioustransparent protective films described above. The adhesive for use inthe present invention may also contain a metal compound filler.

The polarizing film and any other optical film or films may be placed onone another to form a laminate. Examples of such other optical filmsinclude a reflector, a transflector, a retardation plate (including awavelength plate such as a half or quarter wavelength plate), a viewingangle compensation film, a brightness enhancement film, and any otheroptical layer that can be used to form a liquid crystal display deviceor the like. One or more layers of any of these optical components maybe used together with the polarizing film to form a laminate forpractical use.

The optical film including a laminate of the polarizing film and theoptical layer may be formed by a method of stacking them one by one inthe process of manufacturing a liquid crystal display device or thelike. However, an optical film formed in advance by lamination isadvantageous in that it can facilitate the process of manufacturing aliquid crystal display device or the like because it has stable qualityand good assembling workability. In the lamination, any appropriatebonding means such as a pressure-sensitive adhesive layer may be used.When the polarizing film and any other optical layer are bondedtogether, their optical axes may be each aligned at an appropriateangle, depending on the desired retardation properties or other desiredproperties.

The pressure-sensitive adhesive layer-bearing polarizing film of thepresent invention is preferably used to form a variety of image displaydevices such as liquid crystal display devices. Liquid crystal displaydevices may be formed according to conventional techniques.Specifically, a liquid crystal display device may be typically formedusing any conventional technique including properly assembling a displaypanel such as a liquid crystal cell, a pressure-sensitive adhesivelayer-bearing polarizing film, and optional components such as lightingsystem components, and incorporating a driving circuit, except that thepressure-sensitive adhesive layer-bearing polarizing film used isaccording to the present invention. The liquid crystal cell to be usedmay also be of any type such as TN type, STN type, Π type, VA type, orIPS type.

Any desired liquid crystal display device may be formed, such as aliquid crystal display device including a display panel such as a liquidcrystal cell and the pressure-sensitive adhesive layer-bearing opticalfilm or films placed on one or both sides of the display panel, or aliquid crystal display device further including a backlight or areflector in a lighting system. In such a case, the pressure-sensitiveadhesive layer-bearing polarizing film or films according to the presentinvention may be placed on one or both sides of a display panel such asa liquid crystal cell. When the optical films are provided on bothsides, they may be the same or different. The process of forming aliquid crystal display device may also include placing an appropriatecomponent such as a diffusion plate, an antiglare layer, ananti-reflection film, a protective plate, a prism array, a lens arraysheet, a light diffusion plate, or a backlight in one or more layers atan appropriate position or positions.

EXAMPLES

Hereinafter, the present invention will be more specifically describedwith reference to examples, which, however, are not intended to limitthe present invention. In each example, “parts” and “%” are all byweight unless otherwise specified.

<Measurement of the Weight Average Molecular Weight of (Meth)Acryl-basedPolymer (A)>

The weight average molecular weight of the (meth)acryl-based polymer (A)was determined using gel permeation chromatography (GPC).

-   -   Analyzer: HLC-8120GPC manufactured by TOSOH CORPORATION    -   Columns: G7000H_(XL)+GMH_(XL)+GMH_(XL), manufactured by TOSOH        CORPORATION    -   Column size: each 7.8 mmΦ×30 cm, 90 cm in total    -   Column temperature: 40° C.    -   Flow rate: 0.8 ml/minute    -   Injection volume: 100 μl    -   Eluent: tetrahydrofuran    -   Detector: differential refractometer (RI)    -   Standard sample: polystyrene

<Preparation of Polarizing Film (1)>

An 80-μm-thick polyvinyl alcohol film was stretched to 3 times betweenrolls different in velocity ratio while it was dyed in a 0.3% iodinesolution at 30° C. for 1 minute. The film was then stretched to a totalstretch ratio of 6 times while it was immersed in an aqueous solutioncontaining 4% of boric acid and 10% of potassium iodide at 60° C. for0.5 minutes. The film was then washed by immersion in an aqueoussolution containing 1.5% of potassium iodide at 30° C. for 10 secondsand then dried at 50° C. for 4 minutes to give a 20-μm-thick polarizer.Saponified triacetylcellulose films each with a thickness of 40 μm werebonded to both sides of the polarizer with a polyvinyl alcohol-basedadhesive to form a polarizing plate. Hereinafter, this product will bereferred to as TAC-based polarizing film (1).

Production Example 1

<Production of Acryl-based Polymer (A-1)>

A reaction vessel equipped with a condenser tube, a nitrogen introducingtube, a thermometer, and a stirrer was charged with 97 parts of butylacrylate, 3 parts of 4-hydroxybutyl acrylate, and 1 part of AIBN (basedon 100 parts (solid basis) of the monomers) as an initiator togetherwith ethyl acetate. The mixture was allowed to react at 60° C. for 7hours under a nitrogen gas stream. Ethyl acetate was then added to thereaction liquid to form a solution containing an acryl-based polymer(A-1) with a weight average molecular weight of 1,000,000 (solidconcentration: 30% by weight).

Production Example 2

<Production of Acryl-based Polymer (A-2)>

A solution of an acryl-based polymer (A-2) with a weight averagemolecular weight of 1,100,000 was prepared as in Production Example 1,except that a monomer mixture containing 95 parts of butyl acrylate, 4.9parts of acrylic acid, and 0.1 parts of 4-hydroxybutyl acrylate was usedinstead.

Example 1

(Preparation of Pressure-sensitive Adhesive Composition)

Based on 100 parts of the solid of the acryl-based polymer (A-1)obtained in Production Example 1, 0.1 part of trimethylolpropanexylylene diisocyanate (Takenate D110N manufactured by Mitsui Chemicals,Inc.), 0.3 part of dibenzoyl peroxide, 0.1 part ofγ-glycidoxypropylmethoxysilane (KBM-403 manufactured by Shin-EtsuChemical Co., Ltd.), 0.5 part of lithiumbis(nonafluorobutanesulfonyl)imide (EF-N445 manufactured by MitsubishiMaterials Electronic Chemicals Co., Ltd.), and 1 part of lithiumbis(trifluoromethanesulfonyl)imide (manufactured by Wako Pure ChemicalIndustries, Ltd.) were added to the acryl-based polymer (A-1) solutionto form an acryl-based pressure-sensitive adhesive solution.

(Production of Pressure-sensitive Adhesive Layer-Bearing Optical Film)

The acryl-based pressure-sensitive adhesive solution was uniformlyapplied to the surface of a silicone release agent-treated polyethyleneterephthalate film (backing) with a fountain coater and then dried in anair circulation-type thermostatic oven at 155° C. for 2 minutes, so thata 20-μm-thick pressure-sensitive adhesive layer was formed on thesurface of the backing. Subsequently, the pressure-sensitive adhesivelayer-bearing separator was bonded to TAC-based polarizing film (1) toform a pressure-sensitive adhesive layer-bearing polarizing film.

Examples 2 to 12 and Comparative Examples 1 to 5

Pressure-sensitive adhesive layer-bearing polarizing films were preparedas in Example 1, except that the amount of each component was changed asshown in Table 1 when each pressure-sensitive adhesive composition wasprepared.

The pressure-sensitive adhesive layer-bearing polarizing films obtainedin the examples and the comparative examples were evaluated as describedbelow. Table 1 shows the evaluation results.

<Surface Resistance (Initial Resistance)>

After the separator film was peeled off from the pressure-sensitiveadhesive layer-bearing polarizing film, the surface resistance (Ω/□) ofthe pressure-sensitive adhesive surface was measured with MCP-HT450manufactured by Mitsubishi Chemical Analytech Co., Ltd.

<Evaluation of Static Electricity-induced Unevenness>

The prepared pressure-sensitive adhesive layer-bearing polarizing filmwas cut into a piece with a size of 100 mm×100 mm, which was then bondedto a liquid crystal panel. The panel was then placed on a backlight witha brightness of 10,000 cd, and the orientation of the liquid crystal wasdisturbed using 5 kV static electricity generated by an electrostaticgenerator ESD (ESD-8012A manufactured by Sanki Electronic IndustriesCo., Ltd.). The time (seconds) required for recovery from theorientation failure-induced display failure was measured with aninstantaneous multichannel photodetector system (MCPD-3000 manufacturedby Otsuka Electronics Co., Ltd) and evaluated according to the criteriabelow.

-   ⊙: Display failure disappeared in a time of less than one second.-   ◯: Display failure disappeared in a time of one second to less than    10 seconds.-   x: Display failure disappeared in a time of 10 seconds or more.

<Surface Resistance (Resistance after Humidity Test)>

The pressure-sensitive adhesive layer-bearing polarizing film obtainedin each of the examples and the comparative examples was placed in athermo-hygrostat at 60° C. and 95% RH. After 48 hours, thepressure-sensitive adhesive layer-bearing polarizing film was taken outand then dried at 60° C. for 2 hours. Subsequently, the separator filmwas peeled off from the pressure-sensitive adhesive layer-bearingpolarizing film, and the surface resistance of the pressure-sensitiveadhesive surface was measured with MCP-HT450 manufactured by MitsubishiChemical Analytech Co., Ltd.

<Durability>

The separator film was peeled off from the pressure-sensitive adhesivelayer-bearing polarizing film obtained in each of the examples and thecomparative examples. The polarizing film was then bonded to anon-alkali glass plate. The resulting laminate was autoclaved at 50° C.and 5 atm for 15 minutes and then stored in a heating oven at 80° C. andstored in a thermo-hygrostat at 60° C. and 90% RH. After 500 hours, thepresence or absence of peeling of the polarizing film was observed. Thecase where no peeling was detected at all was rated as “⊙,” the casewhere peeling occurred at an invisible level was rated as “◯,” the casewhere visible small peeling occurred was rated as “Δ,” and the casewhere significant peeling was observed was rated as “x.”

TABLE 1 Pressure-sensitive adhesive composition (Meth) acryl- IonicIonic Polyether Crosslinking agent (C) Silane based polymer compoundcompound compound Isocyanate coupling (A) (B1) (B2) (E) compoundPeroxide agent (D) Type Parts Type Parts Type Parts Type Parts TypeParts Type Parts Type Parts Example 1 A-1 100 B-1 0.5 B-6 1 C-1 0.1 C-20.3 D-1 0.1 Example 2 A-1 100 B-1 1 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1Example 3 A-1 100 B-2 1 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1 Example 4 A-1 100B-3 1 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1 Example 5 A-1 100 B-4 1 B-6 1 C-10.1 C-2 0.3 D-1 0.1 Example 6 A-1 100 B-5 1 B-6 1 C-1 0.1 C-2 0.3 D-10.1 Example 7 A-1 100 B-1 1 B-7 1 C-1 0.1 C-2 0.3 D-1 0.1 Example 8 A-1100 B-1 2 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1 Example 9 A-1 100 B-1 1 B-6 2C-1 0.1 C-2 0.3 D-1 0.1 Example 10 A-2 100 B-1 1 B-6 1 C-1 0.1 C-2 0.3D-1 0.1 Example 11 A-1 100 B-1 1 B-6 1 E-1 0.1 C-1 0.1 C-2 0.3 D-1 0.1Example 12 A-1 100 B-8 1 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1 Comparative A-1100 B-6 1 C-1 0.1 C-2 0.3 D-1 0.1 Example 1 Comparative A-1 100 B-2 1C-1 0.1 C-2 0.3 D-1 0.1 Example 2 Comparative A-1 100 C-1 0.1 C-2 0.3D-1 0.1 Example 3 Comparative A-1 100 B-1 5 C-1 0.1 C-2 0.3 D-1 0.1Example 4 Comparative A-1 100 B-6 5 C-1 0.1 C-2 0.3 D-1 0.1 Example 5Evaluations Surface resistance Initial surface after humidificationresistance (60° C./90% RH for 48 h) Static elec- Static elec- DurabilityPolarizing tricity-induced tricity-induced Heating Humidification platetype Ω/□ unevenness Ω/□ unevenness 80° C. 60° C./90% RH Example 1TAC-based 5.50E+10 ⊙ 6.00E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 2TAC-based 4.30E+10 ⊙ 3.80E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 3TAC-based 4.20E+10 ⊙ 3.60E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 4TAC-based 3.90E+10 ⊙ 4.00E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 5TAC-based 4.50E+10 ⊙ 2.80E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 6TAC-based 4.70E+10 ⊙ 4.30E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 7TAC-based 4.30E+10 ⊙ 3.80E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 8TAC-based 3.50E+10 ⊙ 2.00E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 9TAC-based 2.50E+10 ⊙ 5.00E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 10TAC-based 5.50E+10 ⊙ 5.50E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 11TAC-based 4.20E+10 ⊙ 3.00E+11 ◯ ⊙ ⊙ polarizing plate (1) Example 12TAC-based 4.00E+10 ⊙ 3.20E+11 ◯ ⊙ ⊙ polarizing plate (1) ComparativeTAC-based 8.10E+10 ⊙ 1.26E+12 X ⊙ ⊙ Example 1 polarizing plate (1)Comparative TAC-based 3.06E+11 ◯ 4.00E+11 ◯ ⊙ ⊙ Example 2 polarizingplate (1) Comparative TAC-based 10¹³ or X 10¹³ or X ⊙ ⊙ Example 3polarizing more more plate (1) Comparative TAC-based 1.50E+10 ⊙ 1.02E+11◯ ◯ X Example 4 polarizing plate (1) Comparative TAC-based 8.90E+09 ⊙1.02E+12 X ◯ X Example 5 polarizing plate (1)

Concerning the ionic compounds shown in Table 1, “B-1” representslithium bis(nonafluorobutanesulfonyl)imide (EF-N445 (trade name)manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.),“B-2” lithium bis(heptafluoropropanesulfonyl)imide (manufactured by WakoPure Chemical Industries, Ltd.), “B-3” lithiumcyclo-hexafluoropropane-1,3-bis(sulfonyl)imide (EF-N₃₀₅ (trade name)manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.),“B-4” 1-butyl-3-methylpyridium bis(nonafluorobutanesulfonyl)imide(BuMePy•N441 (trade name) manufactured by Mitsubishi MaterialsElectronic Chemicals Co., Ltd.), “B-5”1,1,2,2,3,3-hexafluoropropane-1,3-disulfonic acid dilithium salt(EF-3005 (trade name) manufactured by Mitsubishi Materials ElectronicChemicals Co., Ltd.), “B-6” lithium bis(trifluoromethanesulfonyl)imide(manufactured by Wako Pure Chemical Industries, Ltd.), “B-7”1-butyl-3-methylpyridium bis(trifluoromethanesulfonyl)imide (CIL-312(trade name) manufactured by Japan Carlit Co., Ltd.), and “B-8” lithiumnonafluorobutanesulfonyltrifluoromethanesulfonylimide (EF-N145 (tradename) manufactured by Mitsubishi Materials Electronic Chemicals Co.,Ltd.).

Concerning the crosslinking agent (C), “C-1” represents an isocyanatecrosslinking agent manufactured by Mitsui Chemicals, Inc. (TakenateD110N (trade name), trimethylolpropane xylylene diisocyanate) and “C-2”CORONATE L (trade name) manufactured by Nippon Polyurethane IndustryCo., Ltd.

Concerning the silane coupling agent (D), “D-1” represents KBM-403manufactured by Shin-Etsu Chemical Co. , Ltd.

Concerning the polyether compound (E), “E-1” represents SILYL SAT10(trade name) manufactured by Kaneka Corporation.

The invention claimed is:
 1. A pressure-sensitive adhesive compositioncomprising (A) a (meth)acryl-based polymer, (B1) an ionic compoundcomprising a cation component and an anion component having an organicgroup of three or more carbon atoms, and (B2) an ionic compoundcomprising a cation component and an anion component having an organicgroup of two or less carbon atoms, and the anion component having anorganic group of three or more carbon atoms is at least one of anioncomponents represented by formula (1):(C_(n)F_(2n+1)SO₂)₂N⁻  (1) in formula (1), n is an integer of 3 to 10,formula (2):CF₂(C_(m)F_(2m)SO₂)₂N⁻  (2) in formula (2), m is an integer of 2 to 10,formula (3):⁻O₃S(CF₂)_(l)SO₃ ⁻  (3) in formula (3), l is an integer of 3 to 10, andformula (4):(C_(p)F_(2p+1)SO₂)N⁻(C_(q)F_(2q+1)SO₂)  (4) in formula (4), p and q areeach an integer of 2 to
 10. 2. The pressure-sensitive adhesivecomposition according to claim 1, wherein the cation component of atleast one of the ionic compound (B1) and the ionic compound (B2) is alithium cation.
 3. The pressure-sensitive adhesive composition accordingto claim 1, wherein the anion component having an organic group of threeor more carbon atoms is at least one of abis(heptafluoropropanesulfonyl)imide anion, abis(nonafluorobutanesulfonyl)imide anion, acyclo-hexafluoropropane-1,3-bis(sulfonyl)imide anion, and ahexafluoropropane-1,3-disulfonic acid anion.
 4. The pressure-sensitiveadhesive composition according to claim 1, which contains 0.001 to 4parts by weight of the ionic compound (B1) and 0.001 to 4 parts byweight of the ionic compound (B2) based on 100 parts by weight of the(meth)acryl-based polymer (A).
 5. The pressure-sensitive adhesivecomposition according to claim 1, wherein the (meth) acryl-based polymer(A) contains monomer units derived from an alkyl (meth)acrylate and ahydroxyl group-containing monomer.
 6. The pressure-sensitive adhesivecomposition according to claim 1, wherein the (meth) acryl-based polymer(A) contains monomer units derived from an alkyl (meth)acrylate and acarboxyl group-containing monomer.
 7. The pressure-sensitive adhesivecomposition according to claim 1, further comprising a crosslinkingagent (C).
 8. The pressure-sensitive adhesive composition according toclaim 7, which contains 0.01 to 20 parts by weight of the crosslinkingagent (C) based on 100 parts by weight of the (meth)acryl-based polymer(A).
 9. The pressure-sensitive adhesive composition according to claim7, wherein the crosslinking agent (C) is at least one of an isocyanatecompound and a peroxide.
 10. The pressure-sensitive adhesive compositionaccording claim 1, further comprising 0.001 to 5 parts by weight of asilane coupling agent (D) based on 100 parts by weight of the(meth)acryl-based polymer (A).
 11. The pressure-sensitive adhesivecomposition according to claim 1, further comprising 0.001 to 10 partsby weight of a polyether-modified silicone (E) based on 100 parts byweight of the (meth)acryl-based polymer (A).
 12. The pressure-sensitiveadhesive composition according to claim 1, wherein the (meth)acryl-based polymer (A) has a weight average molecular weight of 500,000to 3,000,000.